Cook County’s decades-neglected forest preserves could get a dramatic makeover in the coming years, under a new plan that will be unveiled Friday morning by Cook County Board President Toni Preckwinkle. But it does come with a cost. And that could mean a property tax increase.

“The best source [of financing] is through a property tax increase,“ said Lenore Beyer-Clow, policy director for the non-profit conservancy group Openlands, which was tapped by the county to come up with the 25-year plan. “Whether there’s an appetite for a tax increase is a whole different conversation.”

No firm plans to finance the project have been made, but Openlands estimates it would require a minimum infusion of $40 million a year. Property owners could end up forking over as much as an additional $26.

While designers of century-old preserves were inspired by the burgeoning national parks movement and the urban planning of Chicago visionary Daniel Burnham, in the past there has been limited money and interest in upkeep. Prior caretakers did themselves a disservice by introducing invasive plants — notably, garlic mustard and buckthorn — that have choked out natural prairie vegetation.

Beyer-Clow said Preckwinkle expressed an interest in changing that. Now, in addition to improving the facilities, the hope is to restore the landscape, making the preserves a refuge for native animals and plant species, according to a summary of the plan. Planners also want to grow the 75,000 acres of county preserves by acquiring thousands of acres of nearby lands.

“There was a long time . . . that they were pretty much neglected,” Beyer-Clow said. “If we don’t do something now, because of the years of neglect, we’re going to lose this treasure.”

The $300,000 tab for the Openlands study and resulting plan was picked up by private organizations.